<div class="checkbox-list">
    {volist name='tags' id ='tag'}

    <div class="checkbox-item">
        {if condition="in_array($tag.id,$userTags)"}
        <input class="checkbox" name="tags_id" value="{$tag.id}" type="checkbox" checked>
        {else /}
        <input class="checkbox" name="tags_id" value="{$tag.id}" type="checkbox" >
        {/if}
        <span style="margin-left: 15px;">{$tag.title}</span>
    </div>
    {/volist}


</div>